From the bold vibrancy of its new Start screen, to its new digital assistant, Cortana, Microsoft’s new Windows Phone 8.1 establishes itself as a top-tier smartphone platform.

And that’s critical—especially for an operating system currently holding a market share of less than 4 percent among U.S. smartphone buyers (though to be fair, it’s more popular elsewhere). That’s not to say it leaps ahead of Apple’s iOS or Google’s Android, but neither is it markedly deficient in any one area—although it could always use more, higher-quality apps.

What’s even better? You don’t need to twiddle your thumbs, waiting for your carrier to push Windows Phone 8.1 to your phone months down the road. You can sign up for Windows Phone Preview for Developers—yes, you, a mere consumer—and receive the same bits as the carriers receive, as well as any updates. (Note, however, that you may void your warranty, and you may not receive device-specific drivers right away.)

For those less adventurous, Windows Phone 8.1 will be available to all Windows Phone 8 devices, including the Nokia Lumia line. But you’ll likely have to wait a month or two for your carrier to vet the new, free update.

Image: Michael Homnick

You can choose a photo to be the focal point of the Windows Phone 8.1 main screen. A random scattering of transparent and opaque Live Tiles overlays the photo, in a way that will seem personalized to some, maybe slightly manic to others.

Windows Phone 8.1 gets personal

Windows Phone 8.1 wants to be your personal operating system. Live Tiles will peek through a screen background of your choosing. The new Cortana digital assistant adjusts itself to your needs and priorities, even screening your calls. And when something of import crops up, a notifications pull-down screen summarizes what you need to know. That barely scratches the surface of the upgrade, but the sum of all the parts is this: a palpable warmth about Windows Phone 8.1 that truly sets it apart.

If there was any knock on the Windows Phone 8 Start screen, it might have been that it was too electric. Every Live Tile was brightly colored, many with embedded information scrolling through. There was no obvious focal point.

In all fairness, some of those problems still remain. But my god, the upgrade’s beautiful. And personalized.

On iOS 7, the home screen is a matrix of flat icons. Microsoft redesigned its Windows Phone 8.1 Live Tiles so that on the Start screen, some would be transparent windows overlaid on a background image of your choosing. You can place a People tile that rolls through photos of your contacts. You can set another tile to flash photos from your Camera Roll. You can pin music, specific people, and even websites to the Start screen, all of which can serve updates.

Some might say it gives the Start screen more of a manic look and feel, but the personal touches make the difference. The Start screen could be just a sterile assembly of code and silicon, but instead, it’s a vibrant, incredibly welcoming front door.

On my Nokia Lumia Icon test unit, supplied by Microsoft, Windows Phone 8.1 allows three columns of large Live Tiles. If there’s any criticism to be made here, it’s that the opacity of the tiles themselves is arbitrary—I couldn’t find a way to enable or customize them.

The lock screen is also customizable to some degree. You can set any number of apps to display on the lock screen, along with the time, date, your next appointment, and the number of unread emails from multiple accounts. Eventually, Microsoft will publish a lock-screen customization app (announced at its recent Build conference), allowing Windows Phone users to create the sort of radically different launcher experiences that Android users can download. But it’s not quite ready, a Microsoft spokeswoman said.

Cortana: Microsoft’s first digital assistant

Cortana, Microsoft’s first digital assistant, is the most dramatic innovation of the Windows Phone 8.1 upgrade. Cast in the mold of Apple’s Siri or Google’s Google Now, and still in beta, Cortana is designed to answer questions and perform simple tasks, such as playing music, setting reminders, or providing directions.

When setting her up, you’re asked to provide a list of topics she can track for you, providing ready updates. You also have the option of letting her peer into your email inbox and other aspects of your digital life, to improve her usefulness to you.

Windows Phone 8.1 offers three ways of accessing Cortana: as a Live Tile, as an app, and by holding down the Search (magnifying-glass) button on the phone itself. The first two methods generate a Cortana screen that includes some brief snippets of headlines. The third takes you directly to a voice-driven interface, where Siri asks and answers questions in a somewhat robotic, female voice.

Image: Michael Homnick

Holding down the Search (magnifying glass) button on the phone calls up the voice-activated version of Cortana.

Word Flow: It works even for sloppy writers

Windows Phone 8.1 also includes Word Flow, essentially Microsoft’s version of Swype (which was bought by Nuance in 2011). Like Swype, you can, well, swipe across the keyboard instead of trying to find the keys.

Quite frankly, I’m horrible at type-by-swipe. My individual fingers know the keys, but when my index finger begins wandering around the screen, it inexplicably loses track of which key is where, and I end up trying to peer around my moving index finger like an idiot. Fortunately, Word Flow was designed with my incompetence in mind. It works. Surprisingly well, in fact. I can use Android’s own type-by-swipe keyboard reasonably well, but I noticed a small improvement while using the Windows keyboard.